JavaScript from Scratch

JavaScript is one of the easiest languages to learn superficially and one of the hardest to truly understand. Most developers can confidently use map, filter, and async/await, yet struggle to explain why code executes in a particular order, what happens to this inside a nested function, or why modifying one object unexpectedly affects another.

This course is built around JavaScript's execution model rather than a list of methods and syntax. You'll learn how the event loop works and why asynchronous operations execute in a predictable yet non-obvious order; how lexical scope works and what closures actually retain in memory; and how prototype-based inheritance powers the class syntax introduced in ES6. This knowledge is far from academic—it is the missing piece behind many bugs that cannot be discovered through logs but become obvious to developers who truly understand how JavaScript works.

Each module concludes with a practical project that requires applying the concepts rather than simply repeating them. You'll implement Promise from scratch, build a state-driven interface without using a framework, and debug a race condition that only appears under a specific sequence of asynchronous operations. By the end of the course, your biggest achievement won't be the list of topics you've covered—it will be the ability to read unfamiliar code and accurately predict what it will do before running it.